{"gene":"DNAJB12","run_date":"2026-06-09T23:54:42","timeline":{"discoveries":[{"year":2010,"finding":"DNAJB12 (JB12) is an ER-localized, single membrane-spanning Hsp40 with its J-domain facing the cytosol. It binds Hsc70 via co-immunoprecipitation, recruits Hsc70 to the ER membrane, and cooperates with cytosolic Hsc70 and the ubiquitin ligase RMA1 to target nascent CFTR and CFTRΔF508 for proteasomal degradation. Overexpression of JB12 accelerates degradation of misfolded membrane proteins (but not misfolded luminal proteins), and knockdown increases CFTR folding efficiency up to threefold.","method":"Protease protection assay, immunofluorescence, co-immunoprecipitation, siRNA knockdown, overexpression with pulse-chase degradation assays, proteasome inhibitor (lactacystin) treatment","journal":"Molecular biology of the cell / Cell structure and function","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, subcellular localization by protease protection and immunofluorescence, functional KD and OE in two independent labs with orthogonal methods","pmids":["21148293","21150129"],"is_preprint":false},{"year":2014,"finding":"Overexpression of DNAJB12 (or DNAJB14) causes formation of elaborate membranous structures (DJANGOS) within the nucleus, connected to the nuclear envelope via a novel nuclear pore configuration. DJANGOS contain DNAJB12, DNAJB14, Hsc70, and ER lumen/membrane markers. Genetic studies showed the chaperone activity of the DNAJ/Hsc70 system is required for DJANGOS formation. These structures dissolve during cell division and reform synchronously in daughter nuclei.","method":"Overexpression, immunofluorescence, electron microscopy (cryo-EM), live-cell imaging, genetic chaperone-activity mutants","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct imaging with EM and live microscopy, genetic validation of chaperone requirement, single lab","pmids":["24732912"],"is_preprint":false},{"year":2017,"finding":"During severe ER stress, DNAJB12 is selectively degraded by the proteasome via ERAD complexes containing HERP, Sel1L, and gp78. JB12 is required to maintain BOK (a pro-apoptotic BCL-2 family member) at low levels; BOK was detected in complexes with JB12 and gp78 by co-immunoprecipitation. Depletion of JB12 leads to BOK accumulation and activation of Caspases 3, 7, and 9, sensitizing cells to proteotoxic and chemotherapeutic agents.","method":"siRNA knockdown, shRNA, proteasome inhibitor treatment, co-immunoprecipitation, caspase activity assays, Western blot","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP identifying complex components, functional KD with caspase readout, single lab with multiple orthogonal methods","pmids":["28536268"],"is_preprint":false},{"year":2021,"finding":"DNAJB12 and cytosolic Hsp70 maintain N1303K-CFTR misfolding intermediates in a detergent-soluble state with a ~3-h half-life. ERAD-resistant pools of N1303K-CFTR concentrate in ER tubules that associate with autophagy initiation sites (WIPI1, FIP200, LC3). Depletion of JB12 prevents entry of N1303K-CFTR into ER-connected phagophore membranes and traffic to autolysosomes. VX-809 stabilization of intermediates promotes their association with autophagy initiation machinery. DNAJB12 operates in biosynthetically active ER microdomains to triage membrane protein intermediates for ERAD versus ER-associated autophagy (ERAA).","method":"siRNA knockdown, detergent solubility assay, immunofluorescence colocalization, half-life/pulse-chase, pharmacological stabilization with VX-809, live imaging","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (biochemical fractionation, genetic KD, imaging, pharmacological intervention) in a single rigorous study with defined pathway placement","pmids":["33534640"],"is_preprint":false},{"year":2021,"finding":"In planthopper vectors of a plant reovirus (SRBSDV), the viral nonstructural protein P7-1 and Hsc70 both directly bind the J-domain of DNAJB12. DNAJB12 overexpression induces ER retention of P7-1, while Hsc70 overexpression promotes transport of P7-1 from the ER to the cytosol for tubule assembly. The DNAJB12-Hsc70 complex is recruited to P7-1 tubules in midgut epithelial cells, and ATPase activity of Hsc70 is required for proper P7-1 tubule assembly. Knockdown of DNAJB12 or Hsc70 strongly inhibits tubule assembly in vivo.","method":"Co-immunoprecipitation/pulldown (direct binding to J-domain), overexpression, siRNA/RNAi knockdown, Hsc70 ATPase inhibitors, immunofluorescence colocalization in infected cells","journal":"Molecular plant pathology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct binding assay mapping J-domain interaction, functional KD, ATPase inhibition, single lab","pmids":["34668642"],"is_preprint":false},{"year":2022,"finding":"DNAJB12 and Hsp70 maintain P23H-rhodopsin (P23H-R) in a detergent-soluble, ERAD-resistant conformation. P23H-R, DNAJB12, and FIP200 colocalize in foci at the rim of WIPI1 omegasome rings. Loss of DNAJB12 function prevents association of P23H-R-containing ER tubules with omegasomes. GABARAP facilitates transfer of P23H-R from ER-connected phagophores to autolysosomes that transiently dock with omegasomes; absence of GABARAP blocks this transfer without interfering with lysosome docking.","method":"DNAJB12 loss-of-function (KD/KO), immunofluorescence colocalization, live imaging, GABARAP genetic manipulation, detergent solubility assays","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic loss-of-function with specific pathway phenotype, multiple colocalization and biochemical methods, defined epistatic relationship with GABARAP, replicated concept across two client proteins","pmids":["35704470"],"is_preprint":false},{"year":2023,"finding":"DNAJB12 and DNAJB14 are structurally similar but non-redundant ER transmembrane Hsp40 co-chaperones. Their DUF1977 ER-lumen domains are dissimilar despite high J-domain homology. Both proteins undergo proteasomal degradation upon acute reductive challenge; DNAJB12 degradation is impaired by sulfenic-acid trapping with dimedone, implicating thiol oxidation in its regulation. Knockdown of DNAJB12 (and DNAJB14 or SGTA) impairs ER-to-cytosol translocation of PDI (ER protein reflux); DNAJB12 (but not DNAJB14) overexpression increases PDI cytosolic relocalization in non-stressed cells.","method":"siRNA knockdown, proteasome inhibitor treatment, dimedone thiol-trapping, subcellular fractionation, Western blot, interactome analysis","journal":"Biochimica et biophysica acta. General subjects","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — biochemical fractionation with genetic KD, chemical trapping for mechanism, single lab with multiple orthogonal methods","pmids":["37925033"],"is_preprint":false},{"year":2023,"finding":"DNAJB12 knockout cells exhibit altered kinetics of phosphorylated Drp1 in response to CCCP-induced mitochondrial stress, and cells depleted of JB12 or JB14 show increased mitochondrial count and branching, suggesting a novel role for DNAJB12 in mitochondrial dynamics under stress.","method":"CRISPR knockout, Western blot for phospho-Drp1, mitochondrial morphology imaging","journal":"Molecular and cellular biochemistry","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, single method per readout, mechanism not fully defined, indirect connection to DNAJB12 function","pmids":["37851175"],"is_preprint":false},{"year":2025,"finding":"DNAJB12 was identified as a direct interactor of the nucleic acid polymer REP 2139 by pulldown. Knockdown of DNAJB12 impedes morphogenesis and secretion of HBV subviral particles (SVPs), HBV virions, and infectious HDV, recapitulating antiviral effects of REP 2139, identifying DNAJB12 as its putative primary target and establishing a functional role for DNAJB12 in HBV/HDV particle morphogenesis.","method":"REP 2139 pulldown/bait identification, siRNA knockdown, viral particle production and secretion assays","journal":"iScience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct binding assay plus functional knockdown with viral production readout, single lab","pmids":["41684842"],"is_preprint":false}],"current_model":"DNAJB12 is an ER-resident, single-pass transmembrane Hsp40 co-chaperone with a cytosol-facing J-domain that recruits cytosolic Hsc70/Hsp70 to the ER membrane; together they triage nascent and misfolded polytopic membrane proteins in a conformation-dependent manner—routing substrates to proteasomal degradation (ERAD) via ubiquitin ligases such as RMA1/gp78, or to ER-associated selective autophagy (ERAA) through omegasome/WIPI1 structures requiring GABARAP—while also controlling the stability of pro-apoptotic BOK and, under reductive ER stress, undergoing thiol-dependent proteasomal self-degradation to promote apoptosis."},"narrative":{"mechanistic_narrative":"DNAJB12 is an ER-resident, single membrane-spanning Hsp40 co-chaperone whose cytosol-facing J-domain recruits cytosolic Hsc70/Hsp70 to the ER membrane to triage misfolded polytopic membrane proteins [PMID:21148293, PMID:21150129]. Acting with Hsc70 and the ubiquitin ligase RMA1, it directs nascent and misfolded membrane substrates such as CFTR and CFTRΔF508 to proteasomal ERAD, with overexpression accelerating degradation of misfolded membrane (but not luminal) proteins and knockdown improving CFTR folding efficiency [PMID:21148293, PMID:21150129]. Beyond ERAD, DNAJB12 and Hsp70 hold ERAD-resistant misfolding intermediates of clients such as N1303K-CFTR and P23H-rhodopsin in a detergent-soluble state within biosynthetically active ER microdomains and route them into ER-associated autophagy (ERAA), where DNAJB12-dependent ER tubules associate with WIPI1 omegasomes and FIP200/LC3 autophagy initiation sites and substrate transfer to autolysosomes requires GABARAP [PMID:33534640, PMID:35704470]. DNAJB12 also controls cell fate during proteotoxic stress: it is itself selectively degraded by gp78/HERP/Sel1L-containing ERAD complexes, maintains the pro-apoptotic BCL-2 protein BOK at low levels, and its depletion drives BOK accumulation and caspase 3/7/9 activation [PMID:28536268]. Its own degradation is regulated by thiol oxidation, being impaired by sulfenic-acid trapping with dimedone, and it promotes ER-to-cytosol reflux of PDI [PMID:37925033]. DNAJB12 has additionally been co-opted by viral systems, serving with Hsc70 as a host factor in plant reovirus P7-1 tubule assembly [PMID:34668642] and in HBV/HDV particle morphogenesis [PMID:41684842].","teleology":[{"year":2010,"claim":"Established that DNAJB12 is an ER membrane Hsp40 that physically recruits cytosolic Hsc70 to triage misfolded membrane proteins, defining its core co-chaperone function in ERAD.","evidence":"Protease protection, immunofluorescence, reciprocal Co-IP, siRNA knockdown and overexpression with pulse-chase degradation of CFTR/CFTRΔF508 in two independent labs","pmids":["21148293","21150129"],"confidence":"High","gaps":["Did not resolve how substrate specificity for membrane vs luminal proteins is achieved","Structural basis of J-domain/Hsc70 engagement not defined"]},{"year":2014,"claim":"Revealed that the DNAJB12/Hsc70 chaperone system can remodel membranes into ordered intranuclear structures (DJANGOS), addressing whether its activity has consequences for membrane architecture.","evidence":"Overexpression with cryo-EM, live-cell imaging, and chaperone-activity mutants in a single lab","pmids":["24732912"],"confidence":"Medium","gaps":["Physiological relevance of overexpression-induced structures unclear","Whether DJANGOS reflect a normal cellular process not established"]},{"year":2017,"claim":"Connected DNAJB12 to apoptotic control by showing it is itself an ERAD substrate during severe stress and gatekeeps the pro-apoptotic protein BOK, defining a stress-sensing role.","evidence":"siRNA/shRNA knockdown, proteasome inhibition, Co-IP of BOK/gp78 complexes, and caspase activity assays in a single lab","pmids":["28536268"],"confidence":"Medium","gaps":["Direct mechanism by which DNAJB12 promotes BOK degradation not resolved","BOK Co-IP not reciprocally validated against structural mapping"]},{"year":2021,"claim":"Placed DNAJB12 at the ERAD-versus-autophagy decision point, showing it maintains soluble client intermediates and is required for their entry into ER-associated autophagy.","evidence":"siRNA knockdown, detergent solubility assays, colocalization with WIPI1/FIP200/LC3, half-life measurements, and VX-809 stabilization of N1303K-CFTR","pmids":["33534640"],"confidence":"High","gaps":["Molecular signal selecting ERAA over ERAD not defined","How DNAJB12-marked tubules dock with autophagy initiation sites unknown"]},{"year":2021,"claim":"Demonstrated direct J-domain binding by a viral protein, establishing DNAJB12/Hsc70 as a host chaperone module exploited for viral structure assembly.","evidence":"Direct J-domain pulldown, overexpression, RNAi knockdown, Hsc70 ATPase inhibition, and colocalization in infected planthopper midgut cells","pmids":["34668642"],"confidence":"Medium","gaps":["Generalizability to mammalian DNAJB12 not addressed","Single lab, single viral system"]},{"year":2022,"claim":"Extended the ERAA model to a second client and defined an epistatic requirement for GABARAP in substrate transfer to autolysosomes, refining pathway architecture.","evidence":"DNAJB12 loss-of-function, colocalization of P23H-rhodopsin with WIPI1 omegasomes/FIP200, live imaging, and GABARAP genetic manipulation","pmids":["35704470"],"confidence":"High","gaps":["Direct DNAJB12-GABARAP relationship not biochemically mapped","Mechanism of omegasome-autolysosome docking not resolved"]},{"year":2023,"claim":"Identified thiol oxidation as a regulator of DNAJB12 turnover and assigned it a role in ER protein reflux, distinguishing it functionally from paralog DNAJB14.","evidence":"siRNA knockdown, proteasome inhibition, dimedone sulfenic-acid trapping, subcellular fractionation of PDI, and interactome analysis","pmids":["37925033"],"confidence":"Medium","gaps":["Specific oxidized cysteine residues not mapped","Mechanism linking DNAJB12 to PDI reflux unknown"]},{"year":2023,"claim":"Raised a possible role for DNAJB12 in stress-induced mitochondrial dynamics, extending its influence beyond the ER.","evidence":"CRISPR knockout, phospho-Drp1 Western blot, and mitochondrial morphology imaging in a single lab","pmids":["37851175"],"confidence":"Low","gaps":["Indirect connection; mechanism not defined","Single method per readout, not independently confirmed"]},{"year":2025,"claim":"Identified DNAJB12 as the direct target of an antiviral nucleic acid polymer and a host factor for HBV/HDV particle morphogenesis, expanding its disease relevance.","evidence":"REP 2139 pulldown bait identification, siRNA knockdown, and viral particle production/secretion assays in a single lab","pmids":["41684842"],"confidence":"Medium","gaps":["Mechanism by which DNAJB12 contributes to particle assembly unknown","Single lab; binding mapping incomplete"]},{"year":null,"claim":"How DNAJB12 mechanistically partitions individual substrates between proteasomal ERAD and ER-associated autophagy, and what structural features of its DUF1977 lumen domain or oxidation-sensitive cysteines govern its regulation, remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of substrate triage","Determinants of ERAD vs ERAA routing undefined","Physiological scope of mitochondrial and viral roles unestablished"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,2,3]},{"term_id":"GO:0044183","term_label":"protein folding chaperone","supporting_discovery_ids":[0,1]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,2]},{"term_id":"GO:0140299","term_label":"molecular sensor activity","supporting_discovery_ids":[6]}],"localization":[{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[0,3,5]},{"term_id":"GO:0005635","term_label":"nuclear envelope","supporting_discovery_ids":[1]}],"pathway":[{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[0,2]},{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[3,5]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[2]},{"term_id":"R-HSA-8953897","term_label":"Cellular responses to stimuli","supporting_discovery_ids":[2,6]}],"complexes":["ERAD complex (HERP/Sel1L/gp78)"],"partners":["HSPA8","RNF5","AMFR","BOK","DNAJB14","GABARAP","SGTA"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9NXW2","full_name":"DnaJ homolog subfamily B member 12","aliases":[],"length_aa":375,"mass_kda":41.9,"function":"Acts as a co-chaperone with HSPA8/Hsc70; required to promote protein folding and trafficking, prevent aggregation of client proteins, and promote unfolded proteins to endoplasmic reticulum-associated degradation (ERAD) pathway (PubMed:21148293, PubMed:21150129). Acts by determining HSPA8/Hsc70's ATPase and polypeptide-binding activities (PubMed:21148293). Can also act independently of HSPA8/Hsc70: together with DNAJB14, acts as a chaperone that promotes maturation of potassium channels KCND2 and KCNH2 by stabilizing nascent channel subunits and assembling them into tetramers (PubMed:27916661). While stabilization of nascent channel proteins is dependent on HSPA8/Hsc70, the process of oligomerization of channel subunits is independent of HSPA8/Hsc70 (PubMed:27916661). When overexpressed, forms membranous structures together with DNAJB14 and HSPA8/Hsc70 within the nucleus; the role of these structures, named DJANGOs, is still unclear (PubMed:24732912) (Microbial infection) In case of infection by polyomavirus, involved in the virus endoplasmic reticulum membrane penetration and infection (PubMed:21673190, PubMed:24675744)","subcellular_location":"","url":"https://www.uniprot.org/uniprotkb/Q9NXW2/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/DNAJB12","classification":"Not Classified","n_dependent_lines":141,"n_total_lines":1208,"dependency_fraction":0.11672185430463576},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"BTF3","stoichiometry":0.2},{"gene":"CANX","stoichiometry":0.2},{"gene":"CAPZB","stoichiometry":0.2},{"gene":"DDOST","stoichiometry":0.2},{"gene":"DIAPH1","stoichiometry":0.2},{"gene":"DNAJC7","stoichiometry":0.2},{"gene":"OST4","stoichiometry":0.2},{"gene":"RER1","stoichiometry":0.2},{"gene":"RPN1","stoichiometry":0.2},{"gene":"RPN2","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/DNAJB12","total_profiled":1310},"omim":[{"mim_id":"621108","title":"DNAJ/HSP40 HOMOLOG, SUBFAMILY C, MEMBER 18; DNAJC2","url":"https://www.omim.org/entry/621108"},{"mim_id":"617487","title":"DNAJ/HSP40 HOMOLOG, SUBFAMILY B, MEMBER 14; DNAJB14","url":"https://www.omim.org/entry/617487"},{"mim_id":"608376","title":"DNAJ/HSP40 HOMOLOG, SUBFAMILY B, MEMBER 12; DNAJB12","url":"https://www.omim.org/entry/608376"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nuclear membrane","reliability":"Supported"},{"location":"Endoplasmic reticulum","reliability":"Supported"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/DNAJB12"},"hgnc":{"alias_symbol":["DJ10","FLJ20027"],"prev_symbol":[]},"alphafold":{"accession":"Q9NXW2","domains":[{"cath_id":"1.10.287.110","chopping":"95-175","consensus_level":"medium","plddt":88.2219,"start":95,"end":175},{"cath_id":"-","chopping":"279-374","consensus_level":"high","plddt":93.4251,"start":279,"end":374},{"cath_id":"1.20.58","chopping":"3-52","consensus_level":"high","plddt":90.441,"start":3,"end":52}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NXW2","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NXW2-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NXW2-F1-predicted_aligned_error_v6.png","plddt_mean":76.31},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=DNAJB12","jax_strain_url":"https://www.jax.org/strain/search?query=DNAJB12"},"sequence":{"accession":"Q9NXW2","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9NXW2.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9NXW2/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NXW2"}},"corpus_meta":[{"pmid":"21148293","id":"PMC_21148293","title":"The endoplasmic reticulum-associated Hsp40 DNAJB12 and Hsc70 cooperate to facilitate RMA1 E3-dependent degradation of nascent CFTRDeltaF508.","date":"2010","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/21148293","citation_count":109,"is_preprint":false},{"pmid":"21150129","id":"PMC_21150129","title":"A novel ER J-protein DNAJB12 accelerates ER-associated degradation of membrane proteins including CFTR.","date":"2010","source":"Cell structure and function","url":"https://pubmed.ncbi.nlm.nih.gov/21150129","citation_count":56,"is_preprint":false},{"pmid":"28536268","id":"PMC_28536268","title":"Endoplasmic reticulum stress-induced degradation of DNAJB12 stimulates BOK accumulation and primes cancer cells for apoptosis.","date":"2017","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/28536268","citation_count":41,"is_preprint":false},{"pmid":"33534640","id":"PMC_33534640","title":"DNAJB12 and Hsp70 triage arrested intermediates of N1303K-CFTR for endoplasmic reticulum-associated autophagy.","date":"2021","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/33534640","citation_count":37,"is_preprint":false},{"pmid":"32801777","id":"PMC_32801777","title":"HNF1A-Induced lncRNA HCG18 Facilitates Gastric Cancer Progression by Upregulating DNAJB12 via miR-152-3p.","date":"2020","source":"OncoTargets and therapy","url":"https://pubmed.ncbi.nlm.nih.gov/32801777","citation_count":36,"is_preprint":false},{"pmid":"24732912","id":"PMC_24732912","title":"Expression of DNAJB12 or DNAJB14 causes coordinate invasion of the nucleus by membranes associated with a novel nuclear pore structure.","date":"2014","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/24732912","citation_count":19,"is_preprint":false},{"pmid":"30349556","id":"PMC_30349556","title":"Environmental Stress Responses of DnaJA1, DnaJB12 and DnaJC8 in Apis cerana cerana.","date":"2018","source":"Frontiers in genetics","url":"https://pubmed.ncbi.nlm.nih.gov/30349556","citation_count":16,"is_preprint":false},{"pmid":"37925033","id":"PMC_37925033","title":"DNAJB12 and DNJB14 are non-redundant Hsp40 redox chaperones involved in endoplasmic reticulum protein reflux.","date":"2023","source":"Biochimica et biophysica acta. General subjects","url":"https://pubmed.ncbi.nlm.nih.gov/37925033","citation_count":13,"is_preprint":false},{"pmid":"34668642","id":"PMC_34668642","title":"A plant reovirus hijacks the DNAJB12-Hsc70 chaperone complex to promote viral spread in its planthopper vector.","date":"2021","source":"Molecular plant pathology","url":"https://pubmed.ncbi.nlm.nih.gov/34668642","citation_count":13,"is_preprint":false},{"pmid":"35704470","id":"PMC_35704470","title":"Lysosome docking to WIPI1 rings and ER-connected phagophores occurs during DNAJB12- and GABARAP-dependent selective autophagy of misfolded P23H-rhodopsin.","date":"2022","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/35704470","citation_count":12,"is_preprint":false},{"pmid":"36743458","id":"PMC_36743458","title":"DNAJB12 and Hsp70 Mediate Triage of Misfolded Membrane Proteins for Proteasomal versus Lysosomal Degradation.","date":"2022","source":"Autophagy reports","url":"https://pubmed.ncbi.nlm.nih.gov/36743458","citation_count":6,"is_preprint":false},{"pmid":"37851175","id":"PMC_37851175","title":"Novel functions of the ER-located Hsp40s DNAJB12 and DNAJB14 on proteins at the outer mitochondrial membrane under stress mediated by CCCP.","date":"2023","source":"Molecular and cellular biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/37851175","citation_count":3,"is_preprint":false},{"pmid":"41684842","id":"PMC_41684842","title":"Unveiling DNAJB12 and DNAJB14 as crucial chaperones in hepatitis B and D virus particle morphogenesis.","date":"2025","source":"iScience","url":"https://pubmed.ncbi.nlm.nih.gov/41684842","citation_count":1,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":9207,"output_tokens":2966,"usd":0.036055,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":10211,"output_tokens":3470,"usd":0.068903,"stage2_stop_reason":"end_turn"},"total_usd":0.104958,"stage1_batch_id":"msgbatch_01AsR7g8dGTEiEw9U83bJeWn","stage2_batch_id":"msgbatch_01YV5ZyxtFNUZEjxRcpd9jzb","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2010,\n      \"finding\": \"DNAJB12 (JB12) is an ER-localized, single membrane-spanning Hsp40 with its J-domain facing the cytosol. It binds Hsc70 via co-immunoprecipitation, recruits Hsc70 to the ER membrane, and cooperates with cytosolic Hsc70 and the ubiquitin ligase RMA1 to target nascent CFTR and CFTRΔF508 for proteasomal degradation. Overexpression of JB12 accelerates degradation of misfolded membrane proteins (but not misfolded luminal proteins), and knockdown increases CFTR folding efficiency up to threefold.\",\n      \"method\": \"Protease protection assay, immunofluorescence, co-immunoprecipitation, siRNA knockdown, overexpression with pulse-chase degradation assays, proteasome inhibitor (lactacystin) treatment\",\n      \"journal\": \"Molecular biology of the cell / Cell structure and function\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, subcellular localization by protease protection and immunofluorescence, functional KD and OE in two independent labs with orthogonal methods\",\n      \"pmids\": [\"21148293\", \"21150129\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Overexpression of DNAJB12 (or DNAJB14) causes formation of elaborate membranous structures (DJANGOS) within the nucleus, connected to the nuclear envelope via a novel nuclear pore configuration. DJANGOS contain DNAJB12, DNAJB14, Hsc70, and ER lumen/membrane markers. Genetic studies showed the chaperone activity of the DNAJ/Hsc70 system is required for DJANGOS formation. These structures dissolve during cell division and reform synchronously in daughter nuclei.\",\n      \"method\": \"Overexpression, immunofluorescence, electron microscopy (cryo-EM), live-cell imaging, genetic chaperone-activity mutants\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct imaging with EM and live microscopy, genetic validation of chaperone requirement, single lab\",\n      \"pmids\": [\"24732912\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"During severe ER stress, DNAJB12 is selectively degraded by the proteasome via ERAD complexes containing HERP, Sel1L, and gp78. JB12 is required to maintain BOK (a pro-apoptotic BCL-2 family member) at low levels; BOK was detected in complexes with JB12 and gp78 by co-immunoprecipitation. Depletion of JB12 leads to BOK accumulation and activation of Caspases 3, 7, and 9, sensitizing cells to proteotoxic and chemotherapeutic agents.\",\n      \"method\": \"siRNA knockdown, shRNA, proteasome inhibitor treatment, co-immunoprecipitation, caspase activity assays, Western blot\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP identifying complex components, functional KD with caspase readout, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"28536268\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"DNAJB12 and cytosolic Hsp70 maintain N1303K-CFTR misfolding intermediates in a detergent-soluble state with a ~3-h half-life. ERAD-resistant pools of N1303K-CFTR concentrate in ER tubules that associate with autophagy initiation sites (WIPI1, FIP200, LC3). Depletion of JB12 prevents entry of N1303K-CFTR into ER-connected phagophore membranes and traffic to autolysosomes. VX-809 stabilization of intermediates promotes their association with autophagy initiation machinery. DNAJB12 operates in biosynthetically active ER microdomains to triage membrane protein intermediates for ERAD versus ER-associated autophagy (ERAA).\",\n      \"method\": \"siRNA knockdown, detergent solubility assay, immunofluorescence colocalization, half-life/pulse-chase, pharmacological stabilization with VX-809, live imaging\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (biochemical fractionation, genetic KD, imaging, pharmacological intervention) in a single rigorous study with defined pathway placement\",\n      \"pmids\": [\"33534640\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"In planthopper vectors of a plant reovirus (SRBSDV), the viral nonstructural protein P7-1 and Hsc70 both directly bind the J-domain of DNAJB12. DNAJB12 overexpression induces ER retention of P7-1, while Hsc70 overexpression promotes transport of P7-1 from the ER to the cytosol for tubule assembly. The DNAJB12-Hsc70 complex is recruited to P7-1 tubules in midgut epithelial cells, and ATPase activity of Hsc70 is required for proper P7-1 tubule assembly. Knockdown of DNAJB12 or Hsc70 strongly inhibits tubule assembly in vivo.\",\n      \"method\": \"Co-immunoprecipitation/pulldown (direct binding to J-domain), overexpression, siRNA/RNAi knockdown, Hsc70 ATPase inhibitors, immunofluorescence colocalization in infected cells\",\n      \"journal\": \"Molecular plant pathology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct binding assay mapping J-domain interaction, functional KD, ATPase inhibition, single lab\",\n      \"pmids\": [\"34668642\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"DNAJB12 and Hsp70 maintain P23H-rhodopsin (P23H-R) in a detergent-soluble, ERAD-resistant conformation. P23H-R, DNAJB12, and FIP200 colocalize in foci at the rim of WIPI1 omegasome rings. Loss of DNAJB12 function prevents association of P23H-R-containing ER tubules with omegasomes. GABARAP facilitates transfer of P23H-R from ER-connected phagophores to autolysosomes that transiently dock with omegasomes; absence of GABARAP blocks this transfer without interfering with lysosome docking.\",\n      \"method\": \"DNAJB12 loss-of-function (KD/KO), immunofluorescence colocalization, live imaging, GABARAP genetic manipulation, detergent solubility assays\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic loss-of-function with specific pathway phenotype, multiple colocalization and biochemical methods, defined epistatic relationship with GABARAP, replicated concept across two client proteins\",\n      \"pmids\": [\"35704470\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"DNAJB12 and DNAJB14 are structurally similar but non-redundant ER transmembrane Hsp40 co-chaperones. Their DUF1977 ER-lumen domains are dissimilar despite high J-domain homology. Both proteins undergo proteasomal degradation upon acute reductive challenge; DNAJB12 degradation is impaired by sulfenic-acid trapping with dimedone, implicating thiol oxidation in its regulation. Knockdown of DNAJB12 (and DNAJB14 or SGTA) impairs ER-to-cytosol translocation of PDI (ER protein reflux); DNAJB12 (but not DNAJB14) overexpression increases PDI cytosolic relocalization in non-stressed cells.\",\n      \"method\": \"siRNA knockdown, proteasome inhibitor treatment, dimedone thiol-trapping, subcellular fractionation, Western blot, interactome analysis\",\n      \"journal\": \"Biochimica et biophysica acta. General subjects\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — biochemical fractionation with genetic KD, chemical trapping for mechanism, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"37925033\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"DNAJB12 knockout cells exhibit altered kinetics of phosphorylated Drp1 in response to CCCP-induced mitochondrial stress, and cells depleted of JB12 or JB14 show increased mitochondrial count and branching, suggesting a novel role for DNAJB12 in mitochondrial dynamics under stress.\",\n      \"method\": \"CRISPR knockout, Western blot for phospho-Drp1, mitochondrial morphology imaging\",\n      \"journal\": \"Molecular and cellular biochemistry\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, single method per readout, mechanism not fully defined, indirect connection to DNAJB12 function\",\n      \"pmids\": [\"37851175\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"DNAJB12 was identified as a direct interactor of the nucleic acid polymer REP 2139 by pulldown. Knockdown of DNAJB12 impedes morphogenesis and secretion of HBV subviral particles (SVPs), HBV virions, and infectious HDV, recapitulating antiviral effects of REP 2139, identifying DNAJB12 as its putative primary target and establishing a functional role for DNAJB12 in HBV/HDV particle morphogenesis.\",\n      \"method\": \"REP 2139 pulldown/bait identification, siRNA knockdown, viral particle production and secretion assays\",\n      \"journal\": \"iScience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct binding assay plus functional knockdown with viral production readout, single lab\",\n      \"pmids\": [\"41684842\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"DNAJB12 is an ER-resident, single-pass transmembrane Hsp40 co-chaperone with a cytosol-facing J-domain that recruits cytosolic Hsc70/Hsp70 to the ER membrane; together they triage nascent and misfolded polytopic membrane proteins in a conformation-dependent manner—routing substrates to proteasomal degradation (ERAD) via ubiquitin ligases such as RMA1/gp78, or to ER-associated selective autophagy (ERAA) through omegasome/WIPI1 structures requiring GABARAP—while also controlling the stability of pro-apoptotic BOK and, under reductive ER stress, undergoing thiol-dependent proteasomal self-degradation to promote apoptosis.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"DNAJB12 is an ER-resident, single membrane-spanning Hsp40 co-chaperone whose cytosol-facing J-domain recruits cytosolic Hsc70/Hsp70 to the ER membrane to triage misfolded polytopic membrane proteins [#0]. Acting with Hsc70 and the ubiquitin ligase RMA1, it directs nascent and misfolded membrane substrates such as CFTR and CFTR\\u0394F508 to proteasomal ERAD, with overexpression accelerating degradation of misfolded membrane (but not luminal) proteins and knockdown improving CFTR folding efficiency [#0]. Beyond ERAD, DNAJB12 and Hsp70 hold ERAD-resistant misfolding intermediates of clients such as N1303K-CFTR and P23H-rhodopsin in a detergent-soluble state within biosynthetically active ER microdomains and route them into ER-associated autophagy (ERAA), where DNAJB12-dependent ER tubules associate with WIPI1 omegasomes and FIP200/LC3 autophagy initiation sites and substrate transfer to autolysosomes requires GABARAP [#3, #5]. DNAJB12 also controls cell fate during proteotoxic stress: it is itself selectively degraded by gp78/HERP/Sel1L-containing ERAD complexes, maintains the pro-apoptotic BCL-2 protein BOK at low levels, and its depletion drives BOK accumulation and caspase 3/7/9 activation [#2]. Its own degradation is regulated by thiol oxidation, being impaired by sulfenic-acid trapping with dimedone, and it promotes ER-to-cytosol reflux of PDI [#6]. DNAJB12 has additionally been co-opted by viral systems, serving with Hsc70 as a host factor in plant reovirus P7-1 tubule assembly [#4] and in HBV/HDV particle morphogenesis [#8].\",\n  \"teleology\": [\n    {\n      \"year\": 2010,\n      \"claim\": \"Established that DNAJB12 is an ER membrane Hsp40 that physically recruits cytosolic Hsc70 to triage misfolded membrane proteins, defining its core co-chaperone function in ERAD.\",\n      \"evidence\": \"Protease protection, immunofluorescence, reciprocal Co-IP, siRNA knockdown and overexpression with pulse-chase degradation of CFTR/CFTR\\u0394F508 in two independent labs\",\n      \"pmids\": [\"21148293\", \"21150129\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve how substrate specificity for membrane vs luminal proteins is achieved\", \"Structural basis of J-domain/Hsc70 engagement not defined\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Revealed that the DNAJB12/Hsc70 chaperone system can remodel membranes into ordered intranuclear structures (DJANGOS), addressing whether its activity has consequences for membrane architecture.\",\n      \"evidence\": \"Overexpression with cryo-EM, live-cell imaging, and chaperone-activity mutants in a single lab\",\n      \"pmids\": [\"24732912\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Physiological relevance of overexpression-induced structures unclear\", \"Whether DJANGOS reflect a normal cellular process not established\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Connected DNAJB12 to apoptotic control by showing it is itself an ERAD substrate during severe stress and gatekeeps the pro-apoptotic protein BOK, defining a stress-sensing role.\",\n      \"evidence\": \"siRNA/shRNA knockdown, proteasome inhibition, Co-IP of BOK/gp78 complexes, and caspase activity assays in a single lab\",\n      \"pmids\": [\"28536268\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct mechanism by which DNAJB12 promotes BOK degradation not resolved\", \"BOK Co-IP not reciprocally validated against structural mapping\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Placed DNAJB12 at the ERAD-versus-autophagy decision point, showing it maintains soluble client intermediates and is required for their entry into ER-associated autophagy.\",\n      \"evidence\": \"siRNA knockdown, detergent solubility assays, colocalization with WIPI1/FIP200/LC3, half-life measurements, and VX-809 stabilization of N1303K-CFTR\",\n      \"pmids\": [\"33534640\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular signal selecting ERAA over ERAD not defined\", \"How DNAJB12-marked tubules dock with autophagy initiation sites unknown\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Demonstrated direct J-domain binding by a viral protein, establishing DNAJB12/Hsc70 as a host chaperone module exploited for viral structure assembly.\",\n      \"evidence\": \"Direct J-domain pulldown, overexpression, RNAi knockdown, Hsc70 ATPase inhibition, and colocalization in infected planthopper midgut cells\",\n      \"pmids\": [\"34668642\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Generalizability to mammalian DNAJB12 not addressed\", \"Single lab, single viral system\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Extended the ERAA model to a second client and defined an epistatic requirement for GABARAP in substrate transfer to autolysosomes, refining pathway architecture.\",\n      \"evidence\": \"DNAJB12 loss-of-function, colocalization of P23H-rhodopsin with WIPI1 omegasomes/FIP200, live imaging, and GABARAP genetic manipulation\",\n      \"pmids\": [\"35704470\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct DNAJB12-GABARAP relationship not biochemically mapped\", \"Mechanism of omegasome-autolysosome docking not resolved\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Identified thiol oxidation as a regulator of DNAJB12 turnover and assigned it a role in ER protein reflux, distinguishing it functionally from paralog DNAJB14.\",\n      \"evidence\": \"siRNA knockdown, proteasome inhibition, dimedone sulfenic-acid trapping, subcellular fractionation of PDI, and interactome analysis\",\n      \"pmids\": [\"37925033\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Specific oxidized cysteine residues not mapped\", \"Mechanism linking DNAJB12 to PDI reflux unknown\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Raised a possible role for DNAJB12 in stress-induced mitochondrial dynamics, extending its influence beyond the ER.\",\n      \"evidence\": \"CRISPR knockout, phospho-Drp1 Western blot, and mitochondrial morphology imaging in a single lab\",\n      \"pmids\": [\"37851175\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Indirect connection; mechanism not defined\", \"Single method per readout, not independently confirmed\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Identified DNAJB12 as the direct target of an antiviral nucleic acid polymer and a host factor for HBV/HDV particle morphogenesis, expanding its disease relevance.\",\n      \"evidence\": \"REP 2139 pulldown bait identification, siRNA knockdown, and viral particle production/secretion assays in a single lab\",\n      \"pmids\": [\"41684842\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which DNAJB12 contributes to particle assembly unknown\", \"Single lab; binding mapping incomplete\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How DNAJB12 mechanistically partitions individual substrates between proteasomal ERAD and ER-associated autophagy, and what structural features of its DUF1977 lumen domain or oxidation-sensitive cysteines govern its regulation, remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model of substrate triage\", \"Determinants of ERAD vs ERAA routing undefined\", \"Physiological scope of mitochondrial and viral roles unestablished\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 2, 3]},\n      {\"term_id\": \"GO:0044183\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 2]},\n      {\"term_id\": \"GO:0140299\", \"supporting_discovery_ids\": [6]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [0, 3, 5]},\n      {\"term_id\": \"GO:0005635\", \"supporting_discovery_ids\": [1]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [0, 2]},\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [3, 5]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [2]},\n      {\"term_id\": \"R-HSA-8953897\", \"supporting_discovery_ids\": [2, 6]}\n    ],\n    \"complexes\": [\"ERAD complex (HERP/Sel1L/gp78)\"],\n    \"partners\": [\"HSPA8\", \"RNF5\", \"AMFR\", \"BOK\", \"DNAJB14\", \"GABARAP\", \"SGTA\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}